diff --git a/js/src/jit/MIR.h b/js/src/jit/MIR.h
index a7574bb5838..2e18e08e66b 100644
--- a/js/src/jit/MIR.h
+++ b/js/src/jit/MIR.h
@@ -3946,7 +3946,6 @@ class MComputeThis
       : MUnaryInstruction(def)
     {
         setResultType(MIRType_Object);
-        setResultTypeSet(def->resultTypeSet());
     }
 
   public: